1. Field of the Invention
The present invention relates to a mechanical power switching apparatus, particularly, to a mechanical power switching apparatus capable of supplying a mechanical power for movement of an optical element constituting a variable focal length optical system, hereinafter referred to as xe2x80x9czoom optical systemxe2x80x9d, and to one or more driving systems for other uses by switching the transmission of the mechanical power generated from a single driving source.
2. Description of the Related Art
Known is, for example, a full automatic camera having an electrically movable zoom lens mounted therein and automatically performing all the operations including the distance measurement, the light measurement, the focus adjustment, the exposure amount control, and the film feeding. A motor for driving a zoom lens barrel and another motor for the film feeding are housed in such a camera.
It should be noted, however, that, in the full automatic camera of the type described above, it is necessary to ensure the space for housing a plurality of motors, which makes it difficult to miniaturize the camera and to lower the manufacturing cost of the camera. In addition, many control circuits and power transistors are required for independently controlling these plural motors, which also makes it difficult to miniaturize the camera and to lower the manufacturing cost of the camera.
A first object of the present invention is to provide a mechanical power switching apparatus capable of supplying the mechanical power generated from a single driving source to a power zoom mechanism for moving optical elements constituting a zoom optical system and also capable of switching the mechanical power supply to one or more driving devices for other uses.
A second object of the present invention is to provide a camera capable of switching the supply of a mechanical power generated from a single actuator to a lens barrel for a zoom motion of the photographing optical system and to one or more driving devices for other uses.
According to a first aspect of the present invention, there is provided a mechanical power switching apparatus, comprising a zoom optical system in which the focal length is changed in accordance with movement of optical elements; a holding mechanism for movably holding said optical elements; a driving source for supplying a mechanical power to said holding mechanism; and a transmission switching mechanism for moving said optical elements, for breaking the transmission of said mechanical power from said driving source to said holding device during the course of change in the focal length of said zoom optical system from the value of 1 to another value, and for transmitting said mechanical power to a driving device for another use differing from the movement of said optical elements.
According to a second aspect of the present invention, there is provided a camera, comprising a zoom photographing optical system in which the focal length is changed in accordance with movement of optical elements; a lens barrel movably holding said optical elements; an actuator for supplying a mechanical power to said lens barrel; and a transmission switching mechanism for moving said optical elements, for breaking the transmission of said mechanical power from said actuator to said lens barrel in accordance with the change in the direction of the mechanical power generated from said actuator during the course of the change in the focal length of said zoom photographing optical system from the value of 1 to another value, and for transmitting said mechanical power to a driving device for another use differing from the movement of said optical elements.
According to the present invention, the mechanical power generated from the driving source can be transmitted to a driving device for another use by changing the direction of the mechanical power generated from the driving source during the course of change in the focal length of the zoom optical system from the value of 1 to another value. Since it is unnecessary to use a plunger or another actuator, it is possible to miniaturize the mechanical power switching apparatus and to manufacture the apparatus with lower manufacturing cost.